Sample Preparation Strategies for PFAS Analysis

Sample preparation takes the spotlight as the panel debates the trade-offs between direct injection and solid-phase extraction (SPE). David Megson recalls trace-level analysis in complex matrices from his postdoc work, describing how adding purification steps to hit low detection limits often meant losing other analytes of interest along the way, a tension especially acute given per- and polyfluoroalkyl substances (PFAS) chemical diversity. Pasquale Avino shares his preference for minimal-pretreatment approaches rooted in his radiochemistry background, explaining that every additional step in sample handling risks introducing artifacts or contamination, though he acknowledges direct injection isn't always practical for PFAS given the need to manage low concentrations.

Bryan Vining describes success using direct injection for difficult matrices like landfill leachate, where sensitive instrumentation allows labs to skip pretreatment altogether and simply dilute and analyze. He notes SPE remains necessary when regulations demand it, when direct injection underperforms, or when detection limits are especially low, but flags a trade-off: SPE removes unwanted interferences while also concentrating them, complicating results. He asks the panel whether there are better ways to approach SPE when it's required.

Megson highlights a caveat around unscreened samples, cautioning that skipping preliminary dilution testing before running SPE can waste both time and sample. He also notes growing interest in proprietary SPE devices designed specifically for PFAS, with vendors experimenting with layering techniques and different solvents, and encourages practitioners to consult directly with method developers rather than troubleshooting alone. Avino agrees that every processing step carries contamination risk, noting that in his experience a universally "golden" extraction method for these compounds doesn't yet exist. Vining sums up the exchange by underscoring that PFAS analysis, more than many other techniques, demands upfront thinking about sample type and objective before any method is chosen.